<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>阴影</title>
    <style>
        div{
            width: 100px;
            height: 100px;
            border: 5px solid red;
            box-shadow: 0px 0px 50px yellow;
        }
    </style>
</head>
<body>
<div></div>

</body>
</html>